Intake air flow rate detection for internal combustion engine

Abstract

An intake air flow rate detection device for an internal combustion engine ( 100 ), including a sensor ( 61, 63 ) that detects an operating condition of the internal combustion engine ( 100 ), an air flow meter ( 21 ) that disposed in the intake passage ( 20 ) upstream of the supercharging device ( 41 ), and a programmable controller ( 60 ) programmed to calculate a measured intake air flow rate from a detection value of the air flow meter ( 21 ), calculate a calculated intake air flow rate from the operating condition of the internal combustion engine ( 100 ), and employ either the measured intake air flow rate or the calculated intake air flow rate as an intake air flow rate of the intake passage ( 20 ) on the basis of an air flow rate of air that is circulated to the intake passage ( 20 ) between the air flow meter ( 21 ) and the supercharging device ( 41 ) through the bypass passage ( 51 ).

1. An intake air flow rate detection device for an internal combustion engine, the engine comprising an intake passage through which intake air flows, a supercharging device that supercharges the intake air, a throttle that throttles the intake air downstream of the supercharging device, a bypass passage that bifurcates between the supercharging device and the throttle and converges with the intake passage upstream of the supercharging device, and a bypass valve that opens and closes the bypass passage, the detection device comprising:
 a sensor that detects an operating condition of the internal combustion engine; 
 an air flow meter disposed in the intake passage upstream of the supercharging device; and 
 a programmable controller programmed to:
 calculate a measured intake air flow rate from a detection value of the air flow meter; 
 calculate a calculated intake air flow rate from the operating condition of the internal combustion engine; and 
 employ either the measured intake air flow rate or the calculated intake air flow rate as an intake air flow rate of the intake passage on the basis of a bypass air flow rate, which is a flow rate of air that is circulated to the intake passage between the air flow meter and the supercharging device through the bypass passage, 
 wherein the controller is further programmed to employ the measured intake air flow rate when the bypass air flow rate is not greater than a threshold value, and employ the calculated intake air flow rate when the bypass air flow rate is greater than the threshold value, the threshold value being a non-zero value beyond which the bypass air flows back to the air flow meter. 
 
 
     
     
       2. The intake air flow rate detection device for an internal combustion engine as defined in  claim 1 , wherein the controller is further programmed to calculate an opening of the bypass valve, employ the measured intake air flow rate as the intake air flow rate when the opening of the bypass valve is smaller than an opening reference value, and employ the calculated intake air flow rate as the intake air flow rate when the opening of the bypass valve is larger than the opening reference value. 
     
     
       3. The intake air flow rate detection device for an internal combustion engine as defined in  claim 2 , wherein the controller is further programmed to increase the opening reference value of the bypass valve as an engine rotation speed increases. 
     
     
       4. The intake air flow rate detection device for an internal combustion engine as defined in  claim 1 , wherein the controller is further programmed to calculate an upper limit value on the basis of the calculated intake air flow rate and an upper limit side correction coefficient, calculate a lower limit value on the basis of the calculated intake air flow rate and a lower limit side correction coefficient, employ the upper limit value as the intake air flow rate when the measured intake air flow rate exceeds the upper limit value, employ the lower limit value as the intake air flow rate when the measured intake air flow rate is lower than the lower limit value, and employ the measured intake air flow rate as the intake air flow rate in all other cases. 
     
     
       5. The intake air flow rate detection device for an internal combustion engine as defined in  claim 1 , wherein the controller is further programmed to calculate the calculated intake air flow rate on the basis of a throttle opening and an engine rotation speed. 
     
     
       6. The intake air flow rate detection device for an internal combustion engine as defined in  claim 1 , wherein the controller is programmed to:
 when a vehicle in which the detection device is located is decelerating, employ either the measured intake air flow rate or the calculated intake air flow rate as an intake air flow rate of the intake passage on the basis of the bypass air flow rate, and 
 when the vehicle is not decelerating, employ the measured intake air flow rate. 
 
     
     
       7. The intake air flow rate detection device for an internal combustion engine as defined in  claim 2 , wherein the controller is further programmed to calculate the opening of the bypass valve on the basis of a supercharging pressure in the intake passage on an upstream side of the throttle and a manifold pressure in the intake passage on a downstream side of the throttle. 
     
     
       8. The intake air flow rate detection device for an internal combustion engine as defined in  claim 2 , further comprising a position sensor that detects a position of a valve body of the bypass valve, wherein the controller is further programmed to calculate the opening of the bypass valve from a detection value of the position sensor. 
     
     
       9. An intake air flow rate detection method for an internal combustion engine, the engine comprising an intake passage through which intake air flows, a supercharging device that supercharges the intake air, a throttle that throttles the intake air downstream of the supercharging device, a bypass passage that bifurcates between the supercharging device and the throttle and converges with the intake passage upstream of the supercharging device, and a bypass valve that opens and closes the bypass passage, the method comprising:
 detecting an operating condition of the internal combustion engine; 
 detecting an intake air flow rate using an air flow meter disposed in the intake passage upstream of the supercharging device; 
 calculating a measured intake air flow rate from a detection value of the air flow meter; 
 calculating a calculated intake air flow rate from the operating condition of the internal combustion engine; and 
 employing either the measured intake air flow rate or the calculated intake air flow rate as an intake air flow rate of the intake passage on the basis of a bypass air flow rate, which is a flow rate of air circulated to the intake passage between the air flow meter and the supercharging device through the bypass passage, 
 wherein the employing step comprises employing the measured intake air flow rate when the bypass air flow rate is not greater than a threshold value, and employing the calculated intake air flow rate when the bypass air flow rate is greater than the threshold value, the threshold value being a non-zero value beyond which the bypass air tows back to the air flow meter. 
 
     
     
       10. An intake air flow rate detection device for an internal combustion engine, the engine comprising an intake passage through which intake air flows, a supercharging device that supercharges the intake air, a throttle that throttles the intake air downstream of the supercharging device, a bypass passage that bifurcates between the supercharging device and the throttle and converges with the intake passage upstream of the supercharging device, and a bypass valve that opens and closes the bypass passage, the detection device comprising:
 first means for detecting an operating condition of the internal combustion engine; 
 second means for detecting an intake air flow rate in the intake passage upstream of the supercharging device; 
 third means for calculating a measured intake air flow rate from a detection value of the second means; 
 fourth means for calculating a calculated intake air flow rate from the operating condition of the internal combustion engine; and 
 fifth means for employing either the measured intake air flow rate or the calculated intake air flow rate as an intake air flow rate of the intake passage on the basis of a bypass air flow rate, which is a flow rate of air circulated to the intake passage between the second means and the supercharging device through the bypass passage, 
 wherein the fifth means employs the measured intake air flow rate when the bypass air flow rate is not greater than a threshold value, and employs the calculated intake air flow rate when the bypass air flow rate is greater than the threshold value, the threshold value being a non-zero value beyond which the bypass air flows back to the second means.